钢锭疏松、缩孔的因素分析及对策

本文就舞钢在特厚钢板的生产中 ,钢锭出现的疏松、缩孔问题展开了深入的分析和讨论 ,研究了钢锭存在疏松、缩孔的宏观及微观因素 ,阐述了为减轻乃至消除这些缺陷所采取的工艺手段和实际效果。

Rheological property and drying mechanism of thermoresponsive gelcasting of ZnO

To solve the problem of drying gelcast green body, the thermoresponsive gel system which contains macromonomer graft chains was used in gelcasting of ZnO. The effects of the amount and length of graft chains macromonomer PIPAAm, the total amount of organic matters, and the solid loading on the rheological properties of suspensions were investigated, and the drying mechanism of gelcast green body was analyzed. The results show that ZnO suspensions with the gel system still display shear- thinning rheological behavior, but its viscosity increases with increasing the addition amount and relative molecular mass of PIPAAm graft chain, and the total organic matter content. The PIPAAm graft chains inhibit or even eliminate the formation of the ＂dense layer” on the surface of gelcast ZnO green bodies, and accelerate the drying of green bodies. The introduction of PIPAAm graft chains facilitates the shrinkage of the gelcast ZnO green bodies, which is a feasible method to increase the relative density of green bodies.

急性肠套叠空气灌肠和水压灌肠疗效差异研究

目的:探究急性肠套叠空气灌肠与水压灌肠疗效差异。方法:对本院2016年1月~2019年2月185例急性肠套叠患儿进行研究,分为实验组与对照组,实验组90例行B超监视下温盐水灌肠肠套叠复位法,对照组95例行X线透视下注气肠套叠复位法。观察两组复位成功率、24h复发率、复位时间及复位压力。结果:实验组复位成功率91.1%,对照组93.7%,比较无统计学意义(P>0.05);实验组24h内复发率8.9%,对照组复发率3.2%。比较无统计学意义(P>0.05)实验组复位时间、复位压比较无统计学意义(P>0.05)。结论:急性肠套叠采用B超监视下温盐水灌肠复位法,患儿、家属及医务人员可以免受X线的辐射,避免出现肠穿孔,值得采用。

Effects of pouring temperature and cylinder temperature on microstructures and mechanical properties of rheomoulding AZ91D alloy

An advanced rheomoulder,which is a device in the integration of melting metal,storage,slurry preparation,transportation and injection forming,was introduced and used to manufacture rheomoulding AZ91 D alloy.Effects of pouring temperature and cylinder temperature on microstructures and mechanical properties of rheomoulding AZ91 D alloy were investigated.The results show that the process can obtain such rheomoulding AZ91 D in which primary α-Mg particles are fine,spherical and uniformly distributed in the matrix.With the decrease of pouring temperature,the morphology of primary α-Mg particles changes from coarse rosette-like to fine spherical shape gradually.As the cylinder temperature decreases,the average size of primary α-Mg particles decreases firstly and then substantially maintains stable while the sphericity and solid fraction increase continuously.Also,decreasing pouring temperature or cylinder temperature properly contributes to improving mechanical properties of rheomoulding AZ91 D for the refinement of α-Mg particles and the decrease of porosity fraction.Furthermore,rheomoulding AZ91 D performs much better than thixomoulding,rheo-diecasting and high pressure die-casting（HPDC） in terms of mechanical properties.Compared with HPDC,the tensile strength,yield strength and elongation are increased by 27.8%,15.7% and 121%,respectively.

Study on High Temperature Behaviour of Gussasphalt

Rutting is one of the most damages in the asphalt surfaces for the orthotropic steel bridge decks. With Hamburg wheel tracking device, the suitable test conditions for Gussasphalt in Germany are pointed out, the high temperature behaviour of Gussasphalt with different binders are tested and compared. The polymer modified binder has higher resistance stability to rutting. The retained time and mixed frequency have obvious effects on Gussasphalt behaviour during Gussasphalt retained period.

Rheo-squeeze casting of semi-solid A356 aluminum alloy slurry

The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring temperatures are properly above the liquidus line, for example 630-650 ℃, the slurry with spherical primary α（Al） grains can be prepared under the stirring power of 1.27 kW. The slurry is then homogeneously held for a short time, and the primary α（Al） grains are further ripened and distributed evenly in the slurry. The results of the rheo-squeezed casting experiments show that the injection specific pressure has a great effect on the filling ability of the semi-solid A356 aluminum alloy slurry, and the higher the injection specific pressure is, the better the ability for the slurry to fill the mould cavity is. When the injection specific pressure is equal to or above 34 MPa, the whole and compact rheo-squeezed castings can be obtained. The microstructure of the castings indicates that the shape, size and numbers of the primary α（Al） grains in different parts of the castings are highly consistent. After being held at 535 ℃ for 5 h and then aged at 155 ℃ for 12 h, the ultimate strength of the rheo-squeezed castings can reach 300-320 MPa, the yield strength 230-255 MPa, and the elongation 11%-15%.

Investigation of a spherical-section ultrasound phased array for hepatic ablation

A 3D ultrasound thermal model with a 3D finite element representation for modeling the thermal diffusion effects for hepatic ablation induced by spherical-section ultrasound phased array was developed. The model was first validated against available published measured data in rat liver. Using the validated model,effects of blood perfusion and heating schemes on lesion formation were studied for both single focus and split-focus intensity patterns. It was shown that for single focus sonication pattern the short-duration(～2 s) and high-intensity(～1250 W/cm2) heating scheme can completely reduce the cooling effect of the blood perfusion. The lesion shape and size were significantly altered by perfusion for split-focus pattern even with a rapid heating scheme when the focus spacing was larger than 2.4 mm. Underdosed areas might be present between two foci. Prolonging ex-posure time or shortening focus spacing can reduce the cool region between two foci. In addition,the influences of thermal and acoustic parameters were also studied. When the therapy depth is short(<5 cm) ,the lesion size monotonically increases with increasing attenuation coefficient that ranges from 5.4 to 11 Np/(m?MHz) .

Study on low temperature performance of Gussasphalt on steel decks with hard bitumen

Using a Hamburg wheel-track test device, the resistance to rutting of Gussasphalt is tested and compared. Gussasphalt with hard bitumen has good resistance to rutting. The related resistance abilities to cracking at low temperature of Gussasphalt are tested and compared through flexural experiments and the composite structure fatigue test with temperature dropping. Gussasphalt with high performance polymer modified bitumen has a longer fatigue life and a lower breaking temperature; they can be used in the future surfaces for steel bridge decks in Germany.

Simulation of stray grain formation during unidirectional solidification of IN738LC superalloy

The influence of casting parameters on stray grain formation of a unidirectionally solidified superalloy IN738LC casting with three platforms was investigated by using a 3D cellular automaton-finite element （CAFE） model in CALCOSOFT package. The model was first validated by comparison of the reported grain structure of AI-7%Si （mass fraction） alloy. Then, the influence of pouring temperature, heat flux of the lateral surface, convection heat coefficient of the cooled chill and mean undercooling of the bulk nucleation on the stray grain formation was studied during the unidirectional solidification. The predictions show that the stray grain formation is obviously sensitive to the pouring temperature, heat flux and mean undercooling of the bulk nucleation. However, increasing the heat convection coefficient has little influence on the stray grain formation.

Quantitative analysis of trace levels of β-ionone in water by liquid-liquidphase extraction-gas chromatography-mass spectrometry(LLE-GC-MS)

A simple and rapid technique based on liquid-liquid extraction coupled to gas chromatography-mass spectrometric detection(LLE-GC-MS) was developed for analysis of taste and odour compound β-ionone in water. Instrument parameters including programmed oven temperature, injection temperature and ion source temperature were evaluated and optimized. Effects of extraction time, ionic strength and p H on the detection efficiency were investigated and optimum conditions were 8 min of extraction time, without Na Cl addition at p H=9. Good linearity(R2=0.9997) was obtained when the linear range was 10-500 μg/L. The recoveries of β-ionone in ultrapure water and tap water samples were 88%-95% and 110%-114%, respectively. The relative standard deviations(RSD) were less than 10%. The method detection limit(MDL) and rejection quality level(RQL) were achieved at1.98 μg/L and 6.53 μg/L, respectively. LLE-GC-MS was demonstrated to be a rapid and convenient method for the determination ofβ-ionone in water samples.

Effects of process parameters on warpage of rapid heat cycle moulding plastic part

The effects of process parameters in rapid heat cycle moulding （RHCM） on parts warpage were investigated. A vehicle-used blue-tooth front shell （consisting of ABS material） was considered as a part example manufactured by RHCM method. The corresponding rapid heat response mould with an innovational conformal heating/cooling channel system and a dynamic mould temperature control system based on the Jll-W-160 type precise temperature controller was proposed. During heating/cooling process, the mould was able to be heated from room temperature to 160 ~C in 6 s and then cooled to 80 ~C in 22 s. The effects of processing conditions in RHCM on part warpage were investigated based on the single factor experimental method and Taguchi theory. Results reveal that the elevated mould temperature reduces unwanted freezing during the injection stage, thus improving mouldability and enhancing part quality, whereas the overheated of mould temperature will lead to defective product. The feasible mould temperature scope in RHCM should be no higher than 140 ~C, and the efficient mould temperature scope should be around the polymer heat distortion temperature. Melt temperature as well as injection pressure effects on warpage can be divided into two stages The lower stage gives a no explicit effect on warpage whereas the higher stage leads to a quasi-linear downtrend. But others affect the warpage as a V-type fluctuation, reaching to the minimum around the heat distortion temperature. Under the same mould temperature condition, the effects of process parameters on warpage decrease according to the following order, packing time, packing pressure, melt temperature, injection pressure and cooling time, respectively.

针灸中药结合治疗膝骨关节炎45例疗效观察

目的:观察针灸中药结合治疗膝骨关节炎的临床疗效。方法:将87例患者随机分为两组,治疗组45例用温针火针和骨肽穴注射以及中药内服相结合治疗,对照组42例用温针治疗。结果:治疗组优16例,良24例,优良率88.89%,对照组由优10例,良20例,优良率71.43%,两组优良率比较P<0.05,差异有显著性。结论:针灸中药结合治疗膝骨关节炎疗效优于温针,是治疗膝骨关节安全有效的方法。

Mild hypothermia protects liver against ischemia and reperfusion injury

AIM: To determine whether mild hypothermia could protect liver against ischemia and reperfusion injury in pigs. METHODS: Twenty-four healthy pigs were randomly divided into normothermia, mild hypothermia and normal control groups. The experimental procedure consisted of temporary interruption of blood flow to total hepatic lobe for different lengths of time and subsequent reperfusion. Hepatic tissue oxygen pressure (PtiO2) and aspartate aminotransferase (AST) values were evaluated, and ultrastructural analysis was carried out for all samples. RESULTS: Serum AST was significantly lower, and hepatic PtiO2 values were significantly higher in the mild hypothermia group than in the normothermia group during liver ischemia-reperfusion periods (P= 0.032, P= 0.028). Meanwhile, the histopathologic injury of liver induced by ischemia-reperfusion was significantly improved in the mild hypothermia group, compared with that in the normothermia group. CONCLUSION: Mild hypothermia can protect the liver from ischemia-reperfusion injury in pigs.

Neural Network Approach to Predict Melt Temperature in Injection Molding Processes

Among the processing conditions of injection molding, temperature of the melt entering the mold plays a significant role in determining the quality of molded parts. In our previous research, a neural network was developed to predict the melt temperature in the barrel during the plastication phase. In this paper, a neural network is proposed to predict the melt temperature at the nozzle exit during the injection phase. A typical two-layer neural network with back propagation learning rules is used to model the relationship between input and output in the injection phase. The preliminary results show that the network works well and may be used for on-line optimization and control of injection molding processes.

Effects of ion chemistry and mass on the electrical properties of ion implanted pyrolyzed polyacrylonitrile

This paper describes the conductivity modifications induced by heavy ion implantation in pyrolysis products obtained by thermal treatment of polyacrylonitrile （PAN） thin films at temperatures of 435℃ （PAN435） and 750℃ （PAN750） under vacuum. Ionic species having different chemical reactivities such as Kr, As, Cl. and F ions were utilized to allow interpretation of the conductivity＇ data either in terms of implantation induced molecular rearrangements or in terms of specific chemical doping effects. The temperature dependence of conductivity in the range between 25-3000C followed nearly a simple activation conduction relationship from which the temperature coefficients of resistivity （ct） were determined. In this temperature range, PAN750 provided the smallest α value compared with ion implanted PAN750 or with products obtained at the lower pyrolysis temperature. However. the corresponding lowest rate of conductivity change with temperatures （0.49%/℃） obtained in this study far exceeds the specification value required for thin film resistor applications （〈 0.1%/℃）.

EFFECTS OF INFLAMMATORY CELLS IN COLD AND WARM ISCHEMIA-REPERFUSION INJURY OF THE GRAFTED LIVER

Objective To investigate whether the impairment of grafted livers after transplantation was induced by the same inflammatory cells both in cold and warm ischemia. Methods Male SD rats were divided into two groups at random,24 donor livers in each group were stored in Ringers solution at 4℃ for 120min or 240min of transplantation for blood sample and tissue specimen collection. Results Along with the prolongation of cold and warm ischemia time,the serum ALT,AST and LDH level increased gradually after transplantation.Under light microscopy,some hepatocytes presented necrosis after 3h and 6h of transplantation in cold ischemia,and neutrophilic infiltration in sinusoids were evident.Also,a large number of hepatocytes were necrotic 3h or 6h after transplantation in warm ischemia from NHBDs,and lymphocytic infiltration was evident in the sinusoids.The findings in electron microscopy was as the same as those of light microscopy,and the cells which infiltrated the sinusoids in warm ischemia were identified as T lymphocytes. Conclusion The impairment of grafted livers after transplantation appeared to be induced by two different kinds of inflammatory cells in cold and warm ischemia,that is,neutrophils mediated the cold ischemia-reperfusion,and T lymphocytes mediated the warm ischemia-reperfusion from NHBDs,but these findings are to be comfirmed in further investigations.

Simulation of Non-isothermal Injection Molding for a Non-Newtonian Fluid by Level Set Method

A non-isothermal injection molding process for a non-Newtonian viscous pseudoplastic fluid is simulated.A conservative interface capturing technique and the flow field solving method are coupled to perform a dynamic simulation.The validity of the numerical method is verified by a benchmark problem.The melt interface evolution versus time is captured and the physical quantities such as temperature,velocity and pressure at each time step are obtained with corresponding analysis.A"frozen skin"layer with the thickness increasing versus time during the injection process is found.The fact that the"frozen skin"layer can be reduced by increasing the injection velocity is numerically verified.The fountain flow phenomenon near the melt interface is also captured.Moreover,comparisons with the non-isothermal Newtonian case show that the curvatures of the interface arcs and the pressure contours near the horizontal mid-line of the cavity for the non-Newtonian pseudoplastic case is larger than that for the Newtonian case.The velocity profiles are different at different positions for the non-Newtonian pseudoplastic case,while in the case of Newtonian flow the velocity profiles are parabolic and almost the same at different positions.

Research on application of different particle sizes of cordierite on castable refractory

Effect of different particle sizes of cordierite on properties of castable refractory by different heat treatment temperatures were investigated respectively with mullite and bauxite as raw materials, calcium aluminate cement as binders. After 24 h curing in mould and another 24 h curing at 110 ℃ after demoulding, the specimens were heat treated at 1 000 ℃, 1 300℃ and 1 500℃ for 3 h, respectively. The bulk density （ BD）, permanent linear change （ PLC）, modulus of rupture（MOR） and clod crushing strength（CCS）, thermal expansion coefficient and thermal shock resistance were examined. The results show that there is no obvious effect on adjusting permanent linear change and bulk density of castables by adding different particle sizes of cordierite at low temperature and intermediate temperature. Modulus of rupture of castable increase with the decreasing of the particle sizes of cordierite after heat treated by 1 000 ℃ and 1 300℃. In this experiment, thermal shock resistance of the castable with cordierite whose particle size is 0 - 1 mm is the best.

Study on Preparation of Temperature-sensitive Injectable Hydrogel

To get a sort of new scaffold material for soft tissue reconstruction,we have prepared XLHA-PNIPAAm and XLHA-MC injectable hydrogels through blending crosslinked HA(XLHA) and two temperature-sensitive materials differed in degradation poly(N-isopropylacrylamide)(PNIPAAm) and methylcellulose(MC),respectively.We tested the injectablility,enzymatic biodegradability,temperature-sensitivity,structure cytotoxicity and hemolysis of the two injectable hydrogels.Our research has successfully obtained the preparation condition of XLHA-PNIPAAm injectable hydrogel,and verified that adding non-degradable material PNIPAAm can postpone the degradation of HA more effectively than degradable material MC.PNIPAAm prepared with 5 kGy dose radiation,MBAAm/NIPAAm(M/M)=0.015,monomer concentration=3% produced XLHA-PNIPAAm with slowest enzymatic biodegradability.DSC results showed that temperature-sensitivity of the XLHA-PNIPAAm was more stable than that of XLHA-MC.Two composite hydrogels were qualified in cytotoxicity and hemolysis tests and the biocompatibility of XLHA-PNIPAAm hydrogel showed better than XLHA-MC hydrogel.

Effects of acupuncture plus mild hypothermia on apoptosis-related factors in rats with cerebral ischemia-reperfusion

Objective： To investigate the effect of acupuncture plus mild hypothermia on neurological function impairment score, cerebral infarct size and apoptosis-related factors in cerebral ischemia reperfusion injury（CIRI） rats. Methods： Sixty healthy male Sprague-Dawley（SD） rats were routinely reared for 1 week. Ten rats were randomly selected as the sham operation group and 10 rats as the blank control group, while the remaining 40 rats were subjected to preparing the middle cerebral artery occlusion（MCAO） model by modified filament occlusion method. The 40 MCAO rats were further randomly divided into a model group, an acupuncture group, a mild hypothermia group and an acupuncture plus mild hypothermia group, with 10 rats in each group. Rats in the sham operation group, the blank control group and the model group did not accept treatment except binding; rats in the acupuncture group received acupuncture treatment; rats in the mild hypothermia group received mild hypothermia treatment; rats in the acupuncture plus mild hypothermia group received acupuncture and mild hypothermia treatment. 72 h after the treatment, neurological function impairment score was performed; the infarct area ratio was determined by 2,3,5-tripheyl tetrazolium chloride（TTC） staining; apoptosis of brain cells was observed by TUNEL method; the expressions of Bcl-2, Bax and Caspase-3 were detected by immunohistochemistry.Results： Compared with the blank control group and the sham operation group, the neurological function impairment score, cerebral infarct area ratio, apoptosis, and the expressions of Bax and Caspase-3 in the model group were significantly increased, while the expression of Bcl-2 was significantly decreased, and there were significant between-group differences（all P〈0.05）. After the treatment, there were statistically significant differences among the treatment groups in the neurological function impairment score, cerebral infarct area ratio and apoptosis in the ischemic side of rats, as well as the expressions of Bcl-2, Bax and Caspase-3（all P〈0.05）, and from the figures, tables and statistical analysis, it was found that a better tendency in the acupuncture plus mild hypothermia group than the acupuncture group or mild hypothermia group. Conclusion： Acupuncture plus mild hypothermia can protect the brain cells by improving neurological function impairment, decreasing cerebral infarct area ratio, reducing the number of apoptotic cells in the ischemic area and regulating the expressions of apoptosis related proteins to inhibit apoptosis.